Methods and apparatus for making a non-woven mat continuously from fibers, particularly inorganic fibers such as glass fibers, from fiber containing slurries are well known in the art. For example British Patent Specification No. 1,376,130 discloses a typical system used to make non-woven mats continuously from a fiber containing slurry. It is also known to make reinforced mats containing reinforcing strands comprising a plurality of monofilament fibers bonded together with an insoluble binder as evidenced by the German Offenlegungsschrift 2,354,553 and United States Application Serial No. 518,332, filed Oct. 29, 1974. In these processes the fibrous slurry is distributed over a moving foraminous surface such as a moving mesh belt and the water is sucked through the foraminous surface depositing the fibers in a random manner in a thin layer on the belt to form a mat.
In the systems described above the foraminous surface is typically 10 to 12 feet or more in width to accommodate the maximum width requirements of the finished product. Since the capital expenditure for such a system and the capacity of the system are both quite high, requirements for narrower mats are met by cutting the finished product lengthwise to produce the width desired. Unfortunately, the products on order rarely can be combined in such a manner as to use the full width or essentially the full width being produced on the machine. This means that a surplus strip of material is usually produced which, because of its varying and small widths, cannot be sold. The finished product contains a binder which has been cured in the oven to bond the fibers together in the mat and therefore the surplus strip of mat cannot be recycled back through the system.
Attempts have been made in the past to slit or cut the wet non-woven mat on the foraminous surface before a binder is added and cured, but the results have been unsatisfactory. Whereas the final product can be slit with a rotating knife after having been lifted from a conveyor coming from the drying and curing oven, the wet mat coming off of the formaminous surface is very fragile and pliable and therefore not susceptible to cutting in the same manner as the finished product. The wet mat cannot be cut on the foraminous surface because the foraminous surface is usually a mesh belt made from a plastic material which would be damaged in cutting the mat.
One attempt that has been tried for cutting the mat on the foraminous surface is to mount a jet or nozzle above the mat and direct a high pressure stream of fluid such as water onto the mat to attempt to separate or cut the mat by eroding the fibers away continuously from a specific area of the moving mat. This resulted in forcing the fibers into and through the perforations in the foraminous surface, an unsatisfactory result. The erosion of the fibers was also incomplete, particularly when the mat contained reinforcing fiber strands, and this caused problems when attempts were made to separate the trimmed portion from the main portion of the mat.
The purpose of the present invention is to provide a method and apparatus for overcoming the above problems and for cleanly and economically separating a linear portion of the wet non-woven mat continuously from along one or both edges so that the non-wanted trim can be returned or recycled back as raw material to the mat forming system.